Working a Load From Scratch

[Danderdude]

I've found myself in a quandry, gentlemen. I want to shoot cast through an AK. The problem is that very little load data exists for 7.62x39, and there's really only one cartridge that is dimensionally similar (.30 Herret), which has even less data.

After reviewing the archived threads on the matter, this question was never answered: Where do you start when there's no starting line?

For the record, I'm looking to fire 170gr GC, 185gr GC and possibly 230gr GC or PB boolits. Data for 160gr and lower exists in the Lyman Cast Bullet Handbook #4, which is on its way to me now. I will also be firing 100gr PB plinkers, 120gr GC and 155gr GC.
Powders on hand include 2400, H110, H322, H4895, RL17 and RL19.

[PuppetZ]

The hodgdon data center list a load for a 150 gr jacketed. Since H4895 respond well to reduced loads, I'd start with 50 or 60% of what they list as a starter and see if it cycle the AK. For a heavier bullet, your guess is as good as mine, but I'd work with H4895 too just because it has given me good result with reduced loads. Start low and slow and be very careful.

[Danderdude]

PuppetZ, you bring up another concern.

When working with a lower-pressure round (45k PSI SAAMI, 51k PSI CIP in the case of 7.62x39, but this is a 2009 production rifle, with CIP proof marks), where the normally visible signs of excessive pressure would not manifest, where do you stop?

Would an attempt at using large pistol primers, rather than large rifle, increase the likelyhood of seeing overpressure signs?

[williamwaco]

My answer is that there is always a starting point. Unless you are creating a new wildcat. Even then there is always a cartridge of similar capacity. (Use one with smaller capacity.)

I think you mean when there is no data for a cast bullet of the weight you want to use. If that is what you mean, I approach this by using jacketed bullet data. Select a load for a jacketed bullet of the same or slightly heaver weight maybe +5% heavier.

If possible, select a load that produces a muzzle velocity in the range of or slightly less than you want to achieve. Reduce it by about 5% and start there.

Or buy a copy of QuickLoad:

http://www.neconos.com/category/Software-2

I have never used this software but I hear good reports.

Where do you stop?

If you are loading a low pressure load and are not concerned about pressure, you stop when you achieve your objective for action functioning reliability, accuracy, and minimal leading.


Do not use large pistol primers in a large rifle cartridge.
( I know that people do it all the time. don't be one of them.)


.

[Danderdude]

I think you mean when there is no data for a cast bullet of the weight you want to use.

No, I mean there's no published data for anything over 160gr, period. The closest thing is some 170gr jacketed .30 Herrett data with 3 IMR powders.


Do not use large pistol primers in a large rifle cartridge.

Just a thought, to help gauge the pressure.

[Old Caster]

For one thing, large pistol primers are shorter than pistol primers and can be seated too deep for ignition and they will back up when fired which can cause some leaking. Otherwise pistol primers are not as tough and can't take pressure as well. Some have used pistol primers in BPCR rifles but when using black powder it is impossible to have pressures as high as with smokeless. I don't see any point in using them in any situation even BPCR. -- Bill --

[williamwaco]

No, I mean there's no published data for anything over 160gr, period. The closest thing is some 170gr jacketed .30 Herrett data with 3 IMR powders.



Just a thought, to help gauge the pressure.



The best bet would be to ask for help here.
( Doesn't seem to be working very well does it? That is not normal for this site, maybe everyone is at the lake today.)

This is NOT a recommendation. I am just going to describe what I would do if I were in your position. First: I would forget those heavy bullets. They probably will not stabilize anyway.

But if I were determined to try them, I would select a powder with a moderate burning rate, say IMR 3031 or 4064.

for a 200 grain cast bullet, I would take the starting load for the 160 grain jacketed and cut it in half. I would then work up from there.

If I( was looking for a plinking load, I would start with 6 grains of Unique and work up. I would not exceed about 8 gr Unique in that case size.

I really should spring for the quickload program but I am too tight.

[PuppetZ]

Just thinking out of the box here. An AK is gas operated. Or to put it otherwise, it need a certain *pressure* to cycle the rounds. Start low and find the point where it's operating the action. That will yield a safe load.

Williamwaco way is also a good procedure IMHO.

[303Guy]

The 30-30 is similar if not a little larger in capacity. I have heard of folks using heavier boolits in the SKS but don't remember the details or even how heavy. You could probably use 28grs W748 under a 170gr cast and possibly get 2000fps with it which may be a little too fast for accuracy - I don't know. I do know that load has been used under a 180gr j-word but I have no idea how safe it is. The user did not claim it to be a max load or otherwise.

[Danderdude]

First: I would forget those heavy bullets. They probably will not stabilize anyway.

The rifle has a 1:9.5" twist, which actually lends itself to heavy, slow boolits, according to the Greenhill equation.


I really should spring for the quickload program but I am too tight.

Ditto ditto ditto.

[MikeS]

There's a thread here in the Milsurp forum (I think that's where it is) that has load info you're looking for. If I'm wrong about where it is, just do a search on "7.62x39" and it should be in there. Lots of good info regarding AK's and cast.

[paul h]

For informational purposes only, what I've done in the past in is look at how the powder charges decrease for a given powder as bullet weight increases, interpolate a line for that data and stick on the low side. Let's arbitrarily say data for powder XXX is 32 gr for a 140 gr bullet, 30 gr for a 150 gr, and 28 gr for a 160 gr. One would interpolate 26 gr charge for 170 gr and 24gr charge for 180 gr bullets.

[DrCaveman]

I'd recommend you choose your powders carefully. H110 would definitely not be on MY list for that experiment. Seems like Unique, 2400, and reloder 7 or 9 maybe are popular for this application due to their mid-level burn rates. Accurate 7 or 9 might be good too.

Find the thread 'practical dope on the 7.62x39' and you get a lo better info than I can provide. I am looking to load some of my Lee 200 gr boolits in this cartridge once I 'master' the 160 gr boolits.

[Elkins45]

For informational purposes only, what I've done in the past in is look at how the powder charges decrease for a given powder as bullet weight increases, interpolate a line for that data and stick on the low side. Let's arbitrarily say data for powder XXX is 32 gr for a 140 gr bullet, 30 gr for a 150 gr, and 28 gr for a 160 gr. One would interpolate 26 gr charge for 170 gr and 24gr charge for 180 gr bullets.

That's what I do as well, with the realization that the line probably starts curving a bit out there toward the end.

[geargnasher]

For informational purposes only, what I've done in the past in is look at how the powder charges decrease for a given powder as bullet weight increases, interpolate a line for that data and stick on the low side. Let's arbitrarily say data for powder XXX is 32 gr for a 140 gr bullet, 30 gr for a 150 gr, and 28 gr for a 160 gr. One would interpolate 26 gr charge for 170 gr and 24gr charge for 180 gr bullets.

Yup.


That's what I do as well, with the realization that the line probably starts curving a bit out there toward the end.

Yup again.

Gear

[303Guy]

Yup. I do that too. I did notice that some ball powders produce a rather sharply increasing pressure rise when they get near the top. Even so, one can get a fair estimate on where to start.

A 1 in 10 twist will stabilize a 245gr boolit and it doesn't have to be driven fast to do so (maybe needs to be supersonic). But for a 200gr boolit, I'd say no problems and I have seen loads for that weight on this forum somewhere. The 200gr loads I saw recently were elsewhere and were second hand but look responsible but the developer was not recommending it, just telling what he did.

[44man]

Unless the firing pin is sprung, primer choice will be critical. They have to be tough or you will get slam fires.
Most of our primers are not military tough.
Load one round in the mag, point the gun safe and release the bolt. If it fires find primers or get a sprung pin.

[Larry Gibson]

With the 7.62x39 in he AK you will find that cast bullets heavier than 160 gr usually don't work well. Limitations are the short mag length, the short case neck and the limited cases capacity. The Lee 155 & 160 gr bullets designed for that cartridge work very well. There should be lots of load data for both available through a "search". I suggest your H4895 as the best powder for the application with either of those bullets. Start at 23 gr and work up to 28 gr or 100% load density. I use 28 gr under the 155 gr Lee bullet for about 1850 fps out of my SKS. That load functions and shoots well in AKs also but is a little slower due to their shorter barrels.


You may get the 120 GC bullets to function the action with H110 or H322 but velocity will be high and accuracy probably poor. Sorry no loading data for those.

The 100 PB bullets would do well with 2.7 - 3 gr of Bullseye but the AK will be a bolt action rifle basically.

Larry Gibson